Three U.S. diplomats have in recent days broken with their typical non-political role making what The New York Times termed a "quiet revolt" against President Donald Trump.

The latest was David H. Rank, the chargé d'affaires at the American Embassy in Beijing, who resigned Monday after telling his staff he was unable to defend Trump's withdrawal from the Paris climate accord.

It was Lewis A. Lukens, acting U.S. Ambassador to Great Britain, who Sunday tweeted support to London Mayor Sadiq Khanhours after the president had publicly criticized him after the Saturday night terror attacks in the city.

"It's an extraordinarily unusual situation for the Foreign Service," Nicholas Burns, undersecretary of state for political affairs for President George W. Bush, told the Times. "They pride themselves on being nonpartisan. You serve each president 150 percent."

In addition to the top diplomats' recent actions, 1,000 staff members recently signed a cable to protest plans for a temporary ban on visitors from seven predominantly Muslim countries. A number of top diplomats have resigned as well, and the Trump White House has been slow filling empty slots.

Rank had been scheduled to stay on in China until Trump's nominee as ambassador, Terry Branstad, took over, but told staff he had been asked to convey the White House's views on the climate accord to Chinese officials, but could not bring himself to do it.

"He was a complete pro, extremely well-regarded," Daniel F. Feldman, a former special representative for Afghanistan and Pakistan, told the Times. "In all his years working for me, I never even knew his politics; exactly what you'd hope for from a career Foreign Service officer."

In Lukens' case in London, he was simply doing what ambassadors typically do in such situations: show support for an ally in time of crisis.

"There's no question he used his best judgment yesterday," Burns said of Lukens.